I want to expand on a couple of points from a Stratfor article by George Friedman in which he talks about the use of drones on a modern terrorist war battlefield.  Friedman ultimately finds the utility of relying on drone strikes of dubious value.  Without addressing his utility conclusion, my own conclusion is that drone strikes are a legitimate application of our national defense imperative.

Friedman suggests in a posited anti-drone argument that

What makes unmanned aerial vehicle strikes controversial is that they are used to deliberately target specific individuals…. The modern battlefield—and the ancient as well—has been marked by anonymity.  The enemy was not a distinct individual but an army, and the killing of soldiers in an enemy army did not carry with it any sense of personal culpability.  In general, no individual soldier was selected for special attention, and his death was not an act of punishment.

…the objection is that the use of unmanned aerial vehicles is not so much an act of war as an act of judgment and, as such, violates international law that requires due process for a soldier being judged and executed.

When is the judgment carried out, though?  In a conventional war, an overall judgment is carried out at the war’s outset, with the decision to enter into it, and any enemy or collection of enemies after that entry is shot on sight.  In the terror war, the same total judgment is made as that of the conventional war, differing only in its mechanics—now it’s most often a two-step process.  A secondary judgment is carried out in real time in the terror war that was subsumed into the conventional war’s original judgment: an individual is identified (including being discriminated from an innocent civilian) in real time, within that larger judgment’s framework, and the strike carried out.  But this two-step process is not materially different from the totality of judgment for the conventional war, and it differs not at all from a two-step process often explicitly carried out in a conventional war: consider the capture of a city by ground troops during which the classic house-to-house combat occurs.  The framework judgment—kill the enemy wherever you find him—was carried out at the war’s start.  Now, in the house-to-house environment, the second step is carried out: is this an enemy soldier, or is it an innocent civilian?

Friedman later says

the United States is engaged in a unique sort of war.  Al Qaeda and the allied groups and sympathetic individuals that comprise the international jihadist movement are global, dispersed and sparse.  They are not a hierarchical military organization.  Where conventional forces have divisions and battalions, the global jihadist movement consists primarily of individuals who at times group together into distinct regional franchises, small groups and cells, and frequently even these groups are scattered.
…
The primary unit is the individual, and the individuals—particularly the commanders—isolate themselves and make themselves as difficult to find as possible.  Given their political intentions and resources, sparse forces dispersed without regard to national boundaries use their isolation as the equivalent of technological stealth to make them survivable and able to carefully mount military operations against the enemy at unpredictable times and in unpredictable ways.

I’ll elide the violation of laws of war at which Friedman hints here and focus on the dispersal aspect.  I suggest that this is not so much a unique sort of war as much as it’s an extension of conventional war tactics carried to an extreme, albeit with a unique set of targets and goals.  The terrorists’ dispersal is simply an extension of conventional infantry tactics writ to a global scale.  Prior to the opening of an infantry assault, the attacking force often attempts to infiltrate as much as possible—through stealth—the defenders’ positions before firing the first shot.  The terror war’s terrorist simply carries this to the next logical step: instead of several infantry units, each consisting of a number of individuals doing the infiltrating, the terrorists’ small units now consists of individual terrorists doing the infiltrating—or the plotting of the attack.

In either of these cases, the drone strike is well within the limits of war: it’s a valid means of killing an enemy—here a terrorist, rather than a soldier—when and where he’s been found, and it’s a valid response to catching a terrorist in his infiltration process (at any stage, from planning it to mid-execution) and interrupting his intended assault.